New Light on Bat Navigation

New light on bat navigation described in articles in, ScienceDaily and ScienceShots 22 July 2014, and BBC News 23 July 2014. Bats are well known for finding their way around by echolocation, i.e. using reflected sound waves. This works very well at short ranges, up to 50m, but will not help the bats orientate themselves over long distances. Yet some bats range over hundreds of kilometres during a night’s foraging, and must return to their roosting places by dawn. Previous studies had shown bats can sense the earth’s magnetic field, and that they need to calibrate, or re-set their starting place each evening when they start out foraging, but how do they achieve this? Experiments using mirrors to shift the image of the sun have shown that bats were not orientating themselves to the sight of the sun’s disc in the sky, so what was providing the frame of reference?

Scientists from Queen’s University Belfast and Tel Aviv University studied the greater mouse-eared bat Myotis myotis to see if it was orientating itself to patterns of polarised light in the sky, which are produced at sunset and sunrise by light scattering through the atmosphere. These patterns occur even when the sun is below the horizon, and in cloudy weather, so would be a useful guide whenever bats were leaving and returning to their roosts.

The research team placed bats in boxes which enabled them to look out into the surrounding landscape, but the windows of the box could be manipulated to change the pattern of polarised light. The researchers then moved the bats about 20 km (12.5 miles) away from their roost sites and released them in the middle of the night when the polarisation pattern is no longer visible. Bats that had been in boxes where the polarisation pattern had been manipulated to appear at 90 degrees offset to the real pattern flew off at 90 degrees to bats that had been allowed to see the real pattern.

So far, these bats are the only mammal known to sense polarised light, and the scientists do not yet know how they detect it. Marie Dacke, who studies animal vision at the Lund University in Sweden, explained that insects are known to have special receptors in their eyes for polarised light, “but in birds and fish and so on, we don't really have a clue about how they're able to perceive this kind of light”. She went on to say: “I did not expect them to find that in mammals, such as in a bat. So I thought this was really fascinating. The big challenge will actually be to find the mechanism by which bats are able to do this. There is still a bit to reveal before the full story is known”.

Editorial Comment: Man’s ability to see polarisation patterns depends on external designed technology i.e. Polaroid sunglasses, polarising microscopes, etc. None of these devices evolved by chance. Therefore, we predict that when scientists rise to the challenge and discover the mechanism by which bats sense polarised light, they will find something at least as clever (probably more) as these, and therefore will have no excuse for believing bat vision evolved by chance random processes. Furthermore, it is not enough for the bats to see the polarised pattern. They have to interpret it, and if they are using it to calibrate their magnetic compass they also need the right brain circuity to integrate the information coming from these two senses. Furthermore, the diverse collection of creatures that can sense and use polarised light does not form a neat evolutionary tree. Therefore, the evolutionists have to resort to believing that polarised light sense evolved, de-evolved and re-evolved many times over. However, polarised light sense is more evidence that animals were created in separate kinds as fully formed, functional organisms. With the ability to sense the world by sound, magnetism and polarised light the term “blind as a bat” gets more inappropriate the more we study them, and we suggest substituting “blind as a Dawk”. (Ref. chiroptera, vision, navigation)